Humans are remarkably accurate and precise when walking blindly to a previously viewed target. This complex spatial behavior relies heavily upon the ability to keep track of one's changing location. The proposed research tests the hypothesis that the human parietal cortex plays an important role in updating one's location while walking. It will also investigate properties of the spatial representation constructed in the parietal lobe. The performance of healthy humans and humans with focal brain lesions in the parietal lobe will be compared in behavioral tests of spatial updating. The participants will indicate the location of targets in a variety of ways, some which involve updating self-location (e.g., walking to previously viewed targets) and others which do not (e.g., verbal reports). The long term goal of this research is to come to a more complete understanding of how vision is used to control complex spatial behavior. This research will help develop a more detailed picture of spatial deficits in patients with injuries in the parietal lobe, and ultimately may help psychologists design effective therapies to rehabilitate brain-injured patients.